High pressure pasteurizable/ultra-high pressure sterilizable food processing container and method

ABSTRACT

A method and container capable of withstanding ultra-high pressure sterilization or pasteurization and being used as a retail package. The container includes at least one deformable pressure absorbing fold channel integrally formed therein enabling the container to undergo UHP processing and return substantially to its prior shape. In one embodiment, the container has at least one sidewall with such a fold channel. In a preferred embodiment, the package also has a bottom wall with a fold channel. The container is thermoformed of a sheet that includes at least one oxygen barrier layer and includes a peelable oxygen barrier film covering a container opening. In a preferred method, the container has a plurality of sidewalls with a fold channel therebetween and a bottom with a fold channel thereabout that accommodates compression between 5% and 25% without showing visible damage when subjected to pressures of between 70 ksi and 120 ksi.

CROSS REFERENCE

This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 61/036,327, filed Mar. 13, 2008, the entirety of which is hereby expressly incorporated by reference herein.

FIELD

The present invention relates to a package for food processing, preferably a container, that is configured to withstand the application of a substantially high pressure for the purpose of sterilization or pasteurization of the contents therein while maintaining its structural integrity.

BACKGROUND

High pressure pasteurization and ultra-high pressure sterilization have been used in the past to treat foodstuffs and other organic material to inactivate bacteria, yeast, mold, and the like. Typically, the product being treated is packaged in a pouch that is subjected to extremely high isostatic pressures for a certain period of time that is sufficient to decrease such contamination by sterilizing the product.

In ultra-high pressure sterilization (UHP) or high pressure pasteurization (HPP), the product being treated is typically packaged in a pouch that is subjected to pressures within a pressure vessel or the like of between 70,000 PSI and 150,000 PSI for a sufficient length of time to inactivate such pathogens. The time under pressure typically ranges from at least three minutes to as long as 15 minutes or more. The process is performed an ambient temperature that typically is no greater than about 140° F. (60° C.).

Prior to UHP/HPP processing, the pouches are loaded with product by inserting the product through a seal that is thereafter closed. Unfortunately, as a result of the extremely high pressures used during UHP processing, the pouch seals can become compromised such that pathogens and the like can easily enter the pouch contaminating it. When this happens, it obviously defeats the purpose of UHP processing requiring the compromise pouch to be disposed of.

While there have been many improvements directed to such pouches, they mainly concern reinforcing the seal by enclosing the seal in a shield or a hood to prevent the seal from being compromised during UHP processing. Unfortunately, this significantly increases pouch cost.

Even when the pouches are not compromised during UHP processing, there are disadvantages to the use of pouches. For example, pouches are not always well suited for being displayed in a retail setting at a store, a gas station or the like. In addition, some types of foodstuffs are not particularly well-suited for pouch packaging.

In the past, it is believed that attempts at using substantially rigid, self-supporting plastic containers have not been heretofore successful because the high pressure employed during UHP processing so greatly deforms the container that any attempt to provide an oxygen impermeable seal cannot be adequately maintained. In addition, the resulting deformation that occurs during UHP processing, so adversely affects the appearance of the container that it simply not suitable for retail display.

What is needed is a substantially rigid and self-supporting plastic container that is capable of maintaining and oxygen impermeable barrier after UHP processing. What is also needed is a substantially rigid and self-supporting plastic container that is capable of maintaining an oxygen impermeable barrier after UHP processing while also maintaining its aesthetic appearance so as to be displayable in a retail setting. What is still further needed is such a container that can be used with a removable lid.

SUMMARY

The present invention relates to a container, that can be in the form of a tub or the like, which includes at least one sidewall and a bottom wall interconnected in a manner that defines a food product holding cavity and which is deformable under ultra high pressure (UHP) processing at pressures of between 70,000 PSI and 120,000 PSI while being able to substantially return to pre-UHP processing shape. The container has an opening through which food product is inserted and which employs a film covering the opening that seals food product in the container prior to UHP processing.

The container has at least one side deformation facilitating fold region integrally formed in it that is of arcuate construction that facilitates deformation during UHP processing and which enables the container to snap back to substantially its original shape after processing is completed. The container can also have at least one bottom deformation facilitating fold region formed in it that facilitates deformation during UHP processing and which enables the container to snap back to substantially its original shape after processing is finished. In a preferred embodiment, each fold region is a channel having an arcuate transverse cross sectional configuration.

Such a container is thermoformed of a sheet having a plurality of pairs of layers with at least one of the layers being an oxygen barrier that keeps oxygen from reaching food product in the container after UHP processing. In one embodiment, the sheet includes an oxygen barrier layer sandwiched between an inner and outer layer. In one preferred embodiment, the multi-layer sheet includes a layer of Ethylene Vinyl Alcohol (EVOH) sandwiched between layers of a co-polymer, such as a polypropylene copolymer. The multi-layer sheet can further include additional layers including one or more tie or adhesive layers. The film also includes an oxygen barrier, such as EVOH, that keeps oxygen from reaching food product in the container after UHP processing with the film sealed to the container about the periphery of its opening. In a preferred embodiment, the sidewalls, bottom and fold channels define a container of one-piece, unitary and substantially homogenous construction.

During UHP processing, a plurality of containers each filled with food product and sealed with film are disposed in a pressure vessel and subjected to pressures between 70 kpsi and 120 kpsi causing deformation of between 5% and 25% during sterilization. After removal of the ultra high pressure, the containers snap back or expand back to substantially the same size as prior to processing. Thereafter, a lid can be attached such that the package containing the container, food product, film and lid are ready for retail display and sale.

In use, the lid is removed and the film peeled away to access the sterilized food product within the container. Such food product keeps at least 45 days. In one preferred embodiment, such food product keeps between 45 and 60 days.

DRAWING DESCRIPTION

The drawings illustrate the best mode currently contemplated as practicing the present invention. One or more preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout and in which:

FIG. 1 is a top perspective view taken of a container of the present invention that is configured for use in UHP/HPP processing;

FIG. 2 is a bottom perspective view of the container of FIG. 1;

FIG. 3 is an elevation view of one side of the container of FIG. 1 with a portion of a sidewall of the container broken away to show food product received in the container;

FIG. 4 is a plan view of the a bottom of the container of the present invention;

FIG. 5 illustrates a second perspective view of a preferred embodiment of a container for holding food product during high pressure sterilization/ultra-high pressure pasteurization and enabling it to be thereafter sold in a retail outlet;

FIGS. 6A and 6B are fragmentary cross section views of the container sidewall taken along line 6-6 of FIG. 5 illustrating preferred container sidewall layer configurations;

FIG. 7 is a fragmentary cross sectional view of a pair of container sidewalls and a UHP fold channel before application of pressure;

FIG. 8 is a fragmentary cross sectional view of the pair of container sidewalls and fold channel shown in FIG. 7 during application of pressure;

FIG. 9 is a perspective view of a lid for use with the container of the present invention; and

FIG. 10 illustrates a stacked arrangement of containers of FIG. 1 used in mass UHP processing within a chamber of a UHP processor.

Before explaining each embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

Turning now to FIGS. 1-4, a container 20 for use in high pressure processing of food product 40 (FIG. 3) is shown. Container 20 is configured for use during ultra-high pressure (UHP) sterilization/pasteurization of the food product 40 within the container 20. In operation, container 20 containing food product 40 is subjected to substantially high pressures whereby the food products contained therein are sterilized and/or pasteurized to provide substantially longer shelf life for the food products 40. During UHP processing, the container 20 and food product 40 contained therein are subjected to isostatic pressure such that the pressure that the container 10 and food product 40 therein is subjected to is substantially uniform or the same in all directions. Thereafter, with the container 20 remaining sealed after UHP processing, the container 20 is shipped to a store or the like where it is available for sale providing a point-of-purchase food product package having significantly extended shelf-life.

Container 20 of the present invention includes four sides 22 defining a cavity 24 therebetween. Container 22 further includes an upper surface 26 having a lip 28 disposed thereon and a flange 29 extending therefrom. The upper surface 26 further defines an opening 27 therein for receiving food product in the cavity 24. The configuration of the upper surface 26, namely lip 28 and flange 29, are generally configured enable the container 20 to be nestable with other containers 10 of the kind of the present invention. The flange 28 is configured to provide a seating surface for other nesting containers. Container 20 further includes a bottom surface 41 for supporting food product. In addition, container 20 further comprises four generally vertically extending fold regions 42 disposed between each of sides 22 and a generally horizontally extending fold region 44 disposed along the outer edge of bottom surface 41. The side fold regions 42 and bottom fold region 44 are configured and shaped to allow the container 22 to withstand relatively high pressures during the UHP process.

A film or other seal 46 (FIG. 3) is provided for covering the container opening 27 and upper surface 26 during the UHP process and to serve as an oxygen barrier. Such a film 46 therefore is or includes an oxygen barrier, such as Ethylene Vinyl Alcohol (EVOH) or the like, to prevent oxygen from entering the container 20 during the UHP process. The film 46 remains attached after the UHP process to provide to prevent oxygen from entering the container 20 and coming into contact with the sterilized food product 40 inside the container 20. The film 46 generally includes an adhesive disposed on one side thereof for application to the lip 28 of upper surface 26. Such an adhesive can be a heat or pressure sensitive adhesive that forms a layer or coating on the side of the film 46 that is applied onto an outer top surface of the lip 28 of container 20. The film 46 can also be a heat and pressure sensitive adhesive or other such adhesive capable of operating as intended for use with the present invention. Using such an adhesive to attach the film 46 to the container 20 enables the film 46 to be peelable from the upper surface 26 of the container 20.

A plurality of fold regions 42 are of concave construction and configured to provide container 20 with superior resiliency under high pressure during UHP processing of between 75 kpsi and 250 kpsi. During the UHP processing, the fold regions 42 are configured to allow for a predetermined amount of buckling. In addition, sides 22 are configured to be generally compressed and collapse during application of such high pressures during the UHP process. After completion of the UHP process, the vertical fold regions 42 and sides 22 are configured to snap back into their original positions without suffering any damage thereto. Preferably, however, the fold regions 42 are not permitted to buckle to a completely inside out configuration, but rather, the regions 42 merely indent or elastically deform a relatively small amount during application of pressure during UHP processing.

Bottom fold region 44 likewise can be provided to allow for buckling up during the pressurization of container 20. As such, upon the release of the pressure therefrom upon the completion of UHP processing, region 44 is configured to snap back into its initial position without causing damage thereto. The dimensions of the bottom fold region 44 are partially driven by the depth of the cutter utilized for machining a mold (not shown) for forming the container 20. The bottom fold region 44 dimensions must be of a certain range depending on the size of the container 20 so as to enable the container 20 to buckle an appropriate amount of under pressure during UHP processing. Specifically, for example, if the bottom fold region is too large, the region 44 will not buckle as needed.

As is shown in the drawing figures, each fold region 42 is of recessed construction, preferably being an elongate fold channel 43. In the currently preferred embodiment shown in the drawing figures, each fold region 42 is of concave construction with each fold region 42 being defined by an elongate radiused channel 43 formed in accordance with that discussed above. The same is true for the elongate radiused channel 45 that defines bottom fold region 44 encompassing the bottom 41 of the container 20.

One or more of fold regions 42 can be of radiused construction as is shown in the drawing figures being a channel 43 having a radius, r, before UHP processing which ranges between ¼ inch and about ⅝ inch, depending on factors such as container size, container thickness, container mold manufacturing constraints, and the like. In addition, with regard to fold region 46, the preferred minimum radius for the bottom fold channel 45 is approximately ¼ inch, and the preferred minimum radius is typically driven by the inherent limitations of the cutting tool utilized for machining the container 20. It is presently contemplated that the radiused bottom fold channel 45 also has a radius of between about ¼ inch and about ⅝ inch but can be larger for containers of a size greater than discussed herein. If desired, one or more of the fold channels 43 and/or 45 can be of convex or outwardly bowed construction.

The side fold channels 43 and bottom fold channel 45 each comprise a particular geometry configured to provide the container 10 holding food product 30 with the ability to substantially deform by compressing between 5% and 25% during the pressurization process while maintaining the ability to expand back to its initial shape thereafter. Further, the container 20 is composed of a resilient material configured to maximize the ability of the container 20 to withstand the pressurization process.

During UHP processing, at least part of a gaseous space 50, referred to as headspace 50, between the food product 40 and the overlying film 46 sealed to the container 20 also compresses as the container 20 compresses. In fact, a container 20 constructed in accordance with the present invention deforms, typically by compressing, under pressure causing compressible gas in the headspace 50 to go into solution in the food product 40. Therefore, a container 20 constructed in accordance with the invention can compress during UHP processing in a manner that accommodates the compressibility of any gaseous headspace 50, including the gas in the headspace 50 going into solution in the food product 40, without plastically deforming the container 20, without rupturing the film 46, or without causing the film 46 to peel away from the container 20.

As a result, a container 20 constructed in accordance with the present invention holds food product 40 during UHP processing while also advantageously serving as a point-of-sale food product package. It is also advantageous that the container 20 undergoes UHP processing without substantial damage such that the container 20 shows virtually no visible sign of having undergone UHP processing. In at least one preferred container embodiment, a container 20 constructed in accordance with the present invention suffers no damage after undergoing UHP processing such that the resultant package shows virtually no externally visible sign of having underwent UHP processing.

The container 20 of the present invention is configured to allow for the sterilization/pasteurization of food product 40 contained therein while maintaining the overall integrity of the container itself. Typically, containers 20 of the present invention are loaded into a vessel 51 (FIG. 10) that is then flooded with water 53 and then uniformly and highly pressurized. The pressurization serves to kill any bacteria or other such organisms that may lead to food spoilage to thereby lengthen the effective shelf life of the food product 40 stored in container 20.

The container 20 of the present invention is preferably used to sterilize and lengthen the effective shelf lives of fresh foods such as vegetables and meats. In a preferred embodiment of the present invention, the shelf lives of foods stored and sterilized/pasteurized using container 20 is at least thirty days and preferably between forty five days and ninety days.

With reference to FIGS. 6A and 6B, the container 20 is composed of a multi-layer sheet 70 a or 70 b adapted to provide a high-pressure barrier package. Such sheeting is commonly used in aseptic, “hot fill” and retort packaging applications. In a preferred embodiment of the present invention, container 20 is made from an extruded seven or nine-layer package sheeting having a very strong oxygen and moisture vapor resistant characteristics to provide a relatively long shelf life for items packaged therein. In another preferred embodiment, the container 20 is formed from a five layer sheet.

With reference to FIG. 6A, the multi-layer sheet 70 a or 70 b includes a pair of outer layers 72 and 74 to provide the container 20 with a moisture barrier. These layers 72 and 74 also help provide structural integrity to the container 20 after thermoforming into the desired shape shown in the drawing figures. Outer layers 72 and 74 are preferably comprised of a copolymer such as, for example, polypropylene. An adhesive or tie layer 76 and 78 is provided on one side of each of the outer layers 72 and 74. An oxygen barrier layer 80 is generally disposed between the two adhesive layers. The oxygen barrier layer 80 preferably comprises a layer of Ethylene Vinyl Alcohol (EVOH). The oxygen barrier layer 80 may, alternatively comprise another compound capable of providing an oxygen barrier and withstanding the substantial pressures applied thereto. For example, Polyvinylidene Chloride (PVDC) or Saran may alternatively be used. In addition, other materials may be added to the multi-layer sheet 70 a to enhance the rigidity thereof or to improve other such aspects. In a preferred embodiment, the sidewalls 22, bottom wall 41 and fold channels 42 and 44 define a container 20 of one-piece, unitary and substantially homogenous construction.

The multi-layer sheet 70 b shown in FIG. 6B is similar to the sheet 70 a shown in FIG. 6A but further includes a plurality of additional layers 82 and 84 that can be of polymeric construction, such as a core layer made of a homopolymer or the like. Where of nine-layer construction, there can be additional layers between layers 74, 84 and 72, 82 or between layers 80, 84 and 80, 82.

In a currently preferred container embodiment shown in FIG. 5, the container 20 is integrally formed so as to have both vertical fold channels 43 and a bottom fold channel 45. Such a container 20 is thermoformed from a multi-layer sheet, e.g., sheet 70 a or 70 b, having at least one oxygen impermeable layer 80 that provides an oxygen barrier during HPP processing of food product 40 in the container 20. In a preferred manufacturing method, the container 20 is thermoformed from a sheet 70 a or 70 b having a plurality of pairs, i.e., at least three, layers with at least one of the layers being an oxygen impermeable layer 80, such as the aforementioned EVOH discussed above. A preferred thermoformable multi-layer sheet 70 a or 70 b has a plurality of resilient and deformable or compressible polymeric layers, each of which can be a copolymer, sandwiching an oxygen impermeable layer. One preferred thermoformable sheet material is disclosed above has having a layer of EVOH sandwiched between a pair of layers of polypropylene. There can be an adhesive layer between the EVOH and each sandwiching layer. If desired, as discussed above with regard to FIGS. 6A and 6B, the sheet from which the container 10 is thermoformed can have additional layers.

The thickness of the above-described sheet 70 a or 70 b from which the container 20 is thermoformed varies with container size or capacity. For example, a container 20 having a size ranging between eight ounces and thirty-two ounces has a thickness ranging from twenty-five mils to forty mils. Such a thickness advantageously helps enable the container 20 to withstand HPP food processing at pressures ranging from 80 kpsi all the way up to 120 kpsi. In one HPP food processing method, the container 20 holding food product 40 is processed at a pressure of about 87 kpsi.

In the preferred embodiment shown in the drawing figures, each sidewall 22 is substantially the same size having substantially the same dimensions. The bottom wall 41 can also be of substantially the same size, such as where the container 20 is of substantially square, cube-shaped construction. If desired, each sidewall and bottom wall can deviate from being square, such as by being rectangular. Each sidewall 22 is separated by a corner section that is formed to provide a fold region 42 about which adjacent and opposed corners 54, 56 (FIGS. 7 and 8) of adjacent sidewalls 22 fold and move toward each other or come together during UHP processing.

In a method of using such a container 20 in UHP food processing, formed containers 20 can be stacked, such as for shipment to a processing plant where each container is filled with food product 40 and then sealed with a film 36 that is oxygen impermeable or which has at least one oxygen impermeable layer. In a preferred embodiment, each container 20 is labeled before UHP processing with a product label that facilitates point-of-sale retail distribution and sale of such containers 20. Food product 40 for which the container 20 and method of use is well suited include fresh foods which cannot be sterilized or pasteurized using conventional high temperature sterilization or pasteurization. Examples of types of food product well suited for UHP food processing in a container 20 constructed in accordance with the present invention include meat, raw fish, such as sushi, salsa, hummus, tomatoes, tomato paste, and guacamole. Other types of food product easily damaged by application of high temperatures can also be packaged and processed in such a container 20.

An example of a preferred film 36 is constructed in accordance with that discussed above. Such a film 36 includes a heat and/or pressure activated adhesive so as to be sealed to a top surface 26 of the lip 28 in a manner that provides a peelable film covering. An example of a suitable film is a commercially available heat-sealable lid stock that is of oxygen impermeable construction such as by having an oxygen barrier layer like EVOH.

With reference to FIG. 10, thereafter, a plurality of pairs of sealed and filled containers 20 are placed in a rack 90 (shown in phantom in FIG. 10) that is inserted into a vessel 51 in which water 53 is introduced under pressure during UHP food processing. In a preferred implementation of a method of UHP food processing using a sealed and filled container 20 constructed in accordance with the present invention, a plurality of pairs of sealed and filled containers 20 are placed in rack 90 and inserted into a generally horizontally disposed high pressure vessel 51 of an UHP processing apparatus 55. Thereafter, water 53 is introduced into the vessel 51 under pressure causing each container 20 and the food product 30 sealed therein to be subjected to pressures ranging between 70 kpsi and 120 kpsi at a suitable temperature for a suitable period of time to achieve UHP processing of the food 40 within each container 20.

With reference to FIG. 7, prior to application of such high pressure, each container sidewall 22 and each corresponding fold channel 44 is not deformed with the adjacent opposed sidewall corners 54, 56 spaced apart from each other a first distance, d₁. With reference to FIGS. 5 and 8, during application of UHP high pressure, each container 20 and the food product 40 within each container 20 deforms by being compressed at least 2%. The remainder of the compression is believed to be a function of the volume of headspace 50 between the food product 40 and the type of food product 40 as it pertains to compressible matter in the food product 40 (as most food is made mostly of incompressible water plus a small percentage of other constituents at least some of which are compressible). For example, it is estimated that food product 40 of the type discussed herein is between 5% and 10% compressible with its compressibility typically being a factor of its water content.

As previously mentioned, pressure is applied for a long enough period of time to kill bacteria and/or viruses in the food product 40 in the container 20 sterilizing it and/or pasteurizing it. As pressure is applied, each sidewall 22 bows inwardly and the associated fold channel 43 folds or buckles slightly in the exemplary manner shown in FIG. 8 helping to accommodate for the pressure while preserving the ability of the container 20 to substantially return to its pre-processing shape and appearance. During application of UHP pressure, adjacent opposed sidewall corners 54, 56 are displaced toward each other causing the fold channel 43 to fold or buckle at least slightly reducing the distance, d₂, therebetween to a distance that is less than d₁. For example, where each fold one of the fold channels 43 is of arcuate or radiused construction, the radius of curvature decreases during application of pressure from its radius of curvature when relaxed prior to application of pressure. The same thing happens to the bottom fold channel 45 prior to and during application of pressure.

During UHP processing, at least part of the headspace 50 also compresses as the container 20 compresses. Depending on the type of food product 40 in the container 20, the amount of headspace 50 it required during packaging, and the UHP processing pressure, the container 20 compresses between about 5% and 25%. For example, in one embodiment where salsa or tomato food product is the food product 40 in the container 20, the container 20 compresses about 15% where the UHP processing pressure is about 87 kpsi. During processing, gas in the headspace 50 responds to being compressed by itself compressing with at least some of the gas in the headspace 50 diffusing into the food product 40. Compression of the container 20, gas in the headspace 50 and compressible matter in the food product 40 occurs as a result of the novel construction of the container 20 without plastically deforming the container 20, rupturing the film 46, or causing the film 46 to peel away from the container 20.

Thereafter, the pressure is removed causing each container 20 and the food product 40 within each container 20 to expand back substantially to the size each was prior to UHP processing (e.g. to the shape depicted in FIG. 7) without the exterior showing virtually any visible damage. Where gas in the headspace 50 has diffused into the food product 40 during UHP processing, it can and typically does come out of the diffusion back into the headspace 50. After processing is finished and all of this occurs, the container 20 has no crinkles, no indentions and has substantially the same shape as prior to UHP processing. Additionally, there is neither rupture of the film 46 nor any breach of the seal between the film 46 and the container 20. In one preferred method implementation, the container 20 has no white areas indicative of plastic deformation thereby indicating that only elastic deformation took place during compression of the container 20 during UHPP processing.

In one preferred method implementation, the container 20 and food product 40 within each container 20 is subjected water 53 pressurized to a pressure of about 87 kpsi during UHP processing causing the container 20 to compress about 15%. After the pressure is removed, each container 20 returns to the shape it previously had prior to UHP processing such that only elastic deformation took place during UHP processing. In another preferred implementation, each container 20 and the food product 40 within each container is subjected to isostatic pressure of between 70 kpsi and 120 kpsi causing each container 20 and the food product 40 to compress between 5% and 25%.

After UHP processing, each container 20 is shipped to a place of retail sale, such as a grocery store, gas station, convenience store or the like where it is placed on sale. A purchaser buying a container 20 peels away the film 46 to access the food product 40 within the container 20. As a result of UHP processing, the shelf life of the food product 40 within each container 20 is at least 45 days. In one preferred embodiment and method implementation, shelf life ranges between 45 days and 90 days.

Referring now to FIG. 9, a lid 75 configured for placement over the top upper surface 26 of the container 20 is specifically configured for use with the present invention. In one preferred embodiment, the lid 75 is secured to the upper surface 26 of the container 20 after completion of the high pressure application to the container 20. Such a lid 75 is attached to the container 20 and overlies the film 46 thereby serving as a protective barrier that protects the integrity of the film 46 (and the oxygen impermeable seal it provides). Such a lid 75 can be pre-labeled or a label can be applied after placement of the lid 75 on the container 20. Such a lid 75 is complementarily configured so as to be snapped onto the container 20 having a top wall 77 that overlies the film 46 when the lid is snapped on, first and second side walls 79 and 81 that engage the container top surface 26, and an outwardly extending flange 83. Such a lid 75 is made of a polymeric material, such as a thermoformable plastic or the like, but can be made of any other suitable material.

Various alternatives are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention. Thus, it is also to be understood that, although the foregoing description and drawings describe and illustrate in detail one or more preferred embodiments of the present invention, to those skilled in the art to which the present invention relates, the present disclosure will suggest many modifications and constructions, as well as widely differing embodiments and applications without thereby departing from the spirit and scope of the invention. 

1. A container for use in high pressure sterilization comprised of at least one sidewall and a fold region formed of a multi-layer sheet having an oxygen barrier and a oxygen barrier film sealing an opening thereof.
 2. The high pressure sterilizable container of claim 1 wherein the multi-layer sheet is comprised of a layer of an oxygen barrier material and at least one layer of a polymer.
 3. The high pressure sterilizable container of claim 2 wherein the multi-layer sheet comprises a plurality of outer layers of polypropylene and an inner layer comprised of an oxygen barrier material.
 4. The high pressure sterilizable container of claim 3 wherein the oxygen barrier material comprises one of Ethylene Vinyl Alcohol and Polyvinylidene Chloride.
 5. The high pressure sterilizable container of claim 1 wherein the sidewall and fold region are integrally formed of the multi-layer sheet forming a container of one piece, substantially homogenous and unitary construction to which the oxygen barrier film is attached.
 6. The high pressure sterilizable container of claim 5 wherein the fold region has an arcuate transverse cross-section, is elongate, and extends generally longitudinally.
 7. The high pressure sterilizable container of claim 6 comprising a plurality of sidewalls with a fold region extending therebetween.
 8. The high pressure sterilizable container of claim 7 comprising a plurality of pairs of sidewalls and wherein there is a fold region extending therebetween that comprises a fold channel.
 8. The high pressure sterilizable container of claim 5 wherein the fold region extends generally transversely.
 9. The high pressure sterilizable container of claim 9 further comprising a bottom wherein the fold region extends along a portion of the bottom.
 10. The high pressure sterilizable container of claim 10 wherein the fold region comprises a channel that extends about a portion of the bottom.
 11. A high-pressure container for use in food sterilization comprising: a bottom comprised of a first integrally formed fold region; a plurality of sides extending upwardly from the bottom comprising a second integrally formed fold region; and wherein the container is configured to buckle under the application of high pressure of at least 70 kpsi and return substantially to its initial shape after application of the pressure.
 12. The container of claim 11 wherein the container is composed of a multi-layer sheet material.
 13. The container of claim 12 wherein the multi-layer sheet material includes at least one layer of a co-polymer adapted to serve as a liquid barrier.
 14. The container of claim 13 wherein the co-polymer comprises polypropylene.
 15. The container of claim 13 wherein the multi-layer sheet material includes at least one layer of an oxygen barrier material.
 16. The container of claim 15 wherein the oxygen barrier material comprises EVOH.
 17. The container of claim 11 further comprising a removable film adapted to be secured to the upper surface of the container and configured to serve as an oxygen barrier.
 18. The container of claim 11 further comprising a removable lid secured to the upper surface of the container.
 19. A method of high pressure sterilization of food product comprising the steps of: providing a container having a sidewall and at least one fold region; packaging perishable food product in the container; placing the container in a vessel configured for high pressure sterilization; filling in the vessel with water; and pressurizing the vessel so as to sterilize the food product to a pressure of at least 70 kpsi; wherein the container is configured to buckle during the pressurization of the vessel and return substantially to its initial shape after the pressurizing.
 20. The method of claim 19 wherein the fold region comprises a channel configured to buckle during the pressurizing of the vessel. 